


A Matter of Buoyancy

by archipelago



Category: Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Acutally Sherlock manages to be both himself and nice, F/M, Friendship, He only ruins their date a little bit, Mary is smart and cool, Sherlock sits through a three and a half hour movie, Titanic - Freeform
Language: English
Status: Completed
Published: 2013-01-21
Updated: 2013-01-21
Packaged: 2017-11-26 08:08:48
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 921
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/648410
Author URL: https://archiveofourown.org/users/archipelago/pseuds/archipelago
Summary: <blockquote class="userstuff">
              <p>John and Mary have a date to watch Titanic in 221B.  Naturally, Sherlock joins in.</p><p>The three of them end up discussing whether both Jack and Rose could have fit on the door.</p><p> </p><p>Believe it or not, this fic is not nearly as cracky as it sounds.</p>
            </blockquote>





	A Matter of Buoyancy

**Author's Note:**

> Disclaimer: I own nothing related to Sherlock.

“She jumped back on the ship? That is completely irrational.”

John sighs and sends Mary an apologetic glance. “Yes, Sherlock. Love is completely irrational, well spotted.” He ignores the glare his flatmate sends and him and adds, “I'm so glad you decided to invite yourself on my date.”

“If you'll recall,” Sherlock snipes, curling his legs up onto the seat of his armchair, “I live here. I did not invite myself anywhere. You brought your date into my home.”

“For God's sake--” John starts, but Mary bumps his shoulder against his, shushing him.

“Hush, both of you. I love this part.”

Jack rushes to meet Rose, admonishing her between frantic kisses. Mary smiles and rests her head on John's shoulder; his arm goes around her back. From his chair, Sherlock scoffs as he motions to the screen. “See? Even he agrees with me that she is an idiot.”

“Oh, Sherlock,” Mary says, amusement thick in her voice. “You think everyone is an idiot.”

Sherlock bristles. He was prepared for anger; her laughter perplexes him. “Yes, well. For good reason.”

Mary says nothing, but there is a smile on her face as she turns her attention back to the telly. Sherlock is so thrown by the lack of opposition that he spends the next thirty minutes in silence, stewing. In John's opinion, Mary's complete immunity to Sherlock's Sherlockiness makes her the perfect woman. To top it off, she has managed to shut the man up during a film for a half hour straight. Really, he thinks, he should be planning his proposal _right now_.

The lovers on screen swim through the freezing water to a broken door. They try to both climb on, but only Rose makes it. John shakes his head. “I think if you'd complain about anything, Sherlock, it would be this part.”

Sherlock frowns. “Why?”

“Because!” John looks at the man for a moment, waiting for him to piece it together himself. When he doesn't, John motions to the screen, “Well, look at what's going on. There's plenty of room. They both could fit on the door. It's ridiculous that he dies.”

Mary lifts her head away from his shoulder. “Actually, John, it's not--”

Sherlock interrupts her. “Clever, Mary. Very clever.” He seems pleased, wrapping his arms around his legs and resting his head on his knees. “I wouldn't have expected you to know.”

There is a smile in her voice when she says, “I'm an idiot capable of surprising you, then.”

His eyes move quickly to John and then back to her. “You're not the first.”

John huffs. “Would someone like to explain to me what is going on?”

“Mary would.” Sherlock replies.

John turns to look at his girlfriend, who shrugs bashfully. “It's not a matter of space, but of buoyancy.” She gnaws at her lip before pressing on. “Think of—I don't know, a pool toy. One of those bits of foam you lie on, yeah? If you sit on it by yourself, you float on top of the water, but if you and a mate sit on it...well, it's not as though you sink to the bottom, is it? But you'll both be at least partly submerged.”

“So if they'd both sat on the door...” John begins.

“They'd have both frozen to death.” Sherlock supplies from his chair. “How did you know, Mary?”

She shrugs again. “Common sense, isn't it?”

Sherlock nods and turns his attention back to the telly. “Indeed.”

John sits in stunned silence as both his companions turn back to Titanic without a second thought. He shakes his head and says, “I'm going to make tea. Anyone else want some?”

When no one answers him, he excuses himself to the kitchen. John turns on the kettle and busies himself getting two mugs down from the cupboard. He sets them down and starts to reach for a third, then draws his hand back. There's no honey in the flat, and that's the only way Mary will drink her tea. Just Sherlock and him, then.

The water boils, and John pours it into the mugs, dropping in the tea bags. He puts two sugars into Sherlock's cup and a dash of milk in his own. He gathers up the mugs, walking back into the sitting room to find that his flatmate has vanished and his girlfriend is crying.

John sets down the tea on the coffee table and crouches in front of Mary, who wipes hastily at her face. He grabs one of her hands and says, “I can't leave him alone with anyone for five minutes! What did he say to you?”

Mary brushes an auburn lock behind her ear and sends him a watery smile. “John. He said--” she hiccoughs and runs a hand over her eyes again, “He said that it was bound to happen eventually.”

“What was?”

“That one day you would find someone nearly as interesting as you.” 

With that, Mary's lower lip trembles, and she bursts into tears again. “I'm sorry, I just—what with all you told me about your previous girlfriends, and with him coming back from the dead and everything—I really expected him to hate me, and instead he said _that_ , and coming from him...that's just about the nicest thing.”

John grabs Mary and hugs her close, petting soothing lines down her back. She cries happy tears into his shoulder as he whispers sweet words to her.

His eyes, however, are trained over her shoulder at Sherlock's bedroom. The door is closed.

**Author's Note:**

> Written very quickly when I should be sleeping because I have to work tomorrow ugghhhasodifaslj. If you notice any errors, please let me know so I can correct them.
> 
> I have a whole series of random "Sherlock watches _____ movie" planned in my head--it's a surprisingly fun thing to write!


End file.
